Remove hardcoded version numbers (part 2) and more documentation

The goal is to change the version number for a new release only in
CMakeLists.txt. This is the second step.

This commit also adds a chapter "Migrating Code from FLTK 1.4 to 1.5".

Details:

- documentation/CMakeLists.txt: configure 'version.dox'
- fluid/documentation/CMakeLists.txt: same as above
- documentation/Doxyfile.in: add "Migrating Code from FLTK 1.4 to 1.5"
- documentation/src/index.dox: include 'version.dox' and 'migrating...'
- fluid/documentation/src/index.dox: same as above
- documentation/src/preface.dox: include 'version.dox'
- documentation/version.dox.in: input to CMake configure 'version.dox'
- fluid/documentation/version.dox.in: same as above
- documentation/src/migration_1_4.dox: update links
- documentation/src/migration_1_5.dox: new documentation chapter

3 files changed, 26 insertions, 18 deletions

diff --git a/fluid/documentation/CMakeLists.txt b/fluid/documentation/CMakeLists.txt
index c729aecd9..3bbdcd755 100644
--- a/fluid/documentation/CMakeLists.txt
+++ b/fluid/documentation/CMakeLists.txt
@@ -47,6 +47,13 @@ if(FLTK_BUILD_FLUID_DOCS OR FLTK_BUILD_PDF_DOCS)
     string(REGEX REPLACE " .*$" "" DOXYGEN_VERSION_SHORT ${DOXYGEN_VERSION})
   endif(DOXYGEN_FOUND)
 
+  # configure version.dox (includes the bare FLTK version number)
+  configure_file(
+    ${CMAKE_CURRENT_SOURCE_DIR}/version.dox.in
+    ${CMAKE_CURRENT_BINARY_DIR}/version.dox
+    @ONLY
+  )
+
   # configure copyright.dox (includes current year)
   configure_file(
     ${CMAKE_CURRENT_SOURCE_DIR}/copyright.dox.in
diff --git a/fluid/documentation/src/index.dox b/fluid/documentation/src/index.dox
index 94c47b4c5..6afbbcc1b 100644
--- a/fluid/documentation/src/index.dox
+++ b/fluid/documentation/src/index.dox
@@ -2,27 +2,27 @@
 
 /**
 
- \cond FL_HTML_INDEX
+\cond FL_HTML_INDEX
 
- \mainpage FLUID User Manual
+\mainpage FLUID User Manual
 
 
- <TABLE CELLPADDING="8" CELLSPACING="0" SUMMARY="TITLE BAR" WIDTH="100%" BORDER="0">
- <TR>
-   <TD><CENTER>
-     \image html fluid-128.png
-     \image latex fluid-128.png  "" width=3cm
-   </CENTER></TD>
-   <TD><CENTER>
-     <B>FLUID 1.5.0 User Manual</B>
-
-     By F.&nbsp;Costantini, M.&nbsp;Melcher,
-     A.&nbsp;Schlosser, B.&nbsp;Spitzak and M.&nbsp;Sweet.
-
-     Copyright © 1998 - 2025 by Bill Spitzak and others.
-   </CENTER></TD>
- </TR>
- </TABLE>
+<TABLE CELLPADDING="8" CELLSPACING="0" SUMMARY="TITLE BAR" WIDTH="100%" BORDER="0">
+<TR>
+  <TD><CENTER>
+    \image html fluid-128.png
+    \image latex fluid-128.png  "" width=3cm
+  </CENTER></TD>
+  <TD><CENTER>
+    <B>FLUID \include{doc} version.dox User Manual</B>
+
+    By F.&nbsp;Costantini, M.&nbsp;Melcher,
+    A.&nbsp;Schlosser, B.&nbsp;Spitzak and M.&nbsp;Sweet.
+
+    \include{doc} copyright.dox
+  </CENTER></TD>
+</TR>
+</TABLE>
 
  <TABLE CELLPADDING="8" CELLSPACING="0" SUMMARY="TITLE BAR" WIDTH="100%" BORDER="0">
  <TR>
diff --git a/fluid/documentation/version.dox.in b/fluid/documentation/version.dox.in
new file mode 100644
index 000000000..569b8ea85
--- /dev/null
+++ b/fluid/documentation/version.dox.in
@@ -0,0 +1 @@
+@FLTK_VERSION@